1. Field of the Invention
This invention relates to a process for regeneration of a zeolite catalyst, specifically an aluminosilicate zeolite with germanium substituted in the framework for silicon and with platinum deposited on the zeolite. The catalyst may be used in a process for aromatization of alkanes, e.g. C2-C8.
2. Description of the Prior Art
Zeolites are a crystalline hydrated aluminosilicate that may also contain other metals. The term “zeolite” includes not only aluminosilicates but substances in which the aluminum is replaced by other trivalent elements and substance in which silicon is replaced by other tetravalent elements. Elements may be deposited on the zeolite to enhance properties of a zeolite catalyst used in particular processes.
Zeolites are known catalysts for aromatics in isomerization, toluene disproportionation, transalkylation, hydrogenation and alkane oligomerization and aromatization. Generally, catalysts deactivate when operated under commercial process conditions and must be regenerated to continue to be used in a reaction system.
U.S. Pat. No. 4,806,699 discloses a process for the production of aromatic hydrocarbons from ethane and/or propane and/or butane with a gallium loaded ZSM-5 type aluminosilicate zeolite which is regenerated using a conventional method, e.g. by burning off the deactivating carbon deposited thereon using air diluted with an inert gas, e.g., nitrogen at elevated temperature.
U.S. Pat. No. 5,019,663 discloses aromatization of C3-C4 paraffin-rich streams (commonly known as LPG), in a highly endothermic reaction in a fixed, moving or fluid catalyst bed. For example, the CYCLAR (tradename) process for LPG aromatization uses a plurality of moving-bed reaction zones together with continuous catalyst regeneration (CCR) to supply the required heat for the primary endothermic reaction. This commercial process scheme involving transporting hot catalyst pellets between the reaction and regeneration zones requires extensive capital investment. The CYCLAR (tradename) process is described in the paper “CYCLAR: One Step Processing of LPG to Aromatics and Hydrogen,” by R. F. Anderson, J. A. Johnson and J. R. Mowry presented at the AIChE Spring National Meeting, Houston, Tex., Mar. 24-28, 1985.
U.S. Pat. No. 5,155,075 discloses a process for regeneration of a hydrocarbon reforming catalyst which has been deactivated by buildup of coke. The catalyst is regenerated by a controlled low temperature carbon-burn procedure. In the reactor design, catalyst that is still active, but which has some coke buildup is slowly withdrawn from the bottom of the last reactor stage and transferred to the regeneration section while an equivalent volume of regenerated catalyst is conveyed from the regenerator back to the top of the first reactor. Regeneration consists of the combustion of the deposited coke using high temperature air and/or steam.
U.S. Pat. No. 5,157,183 discloses a process for converting low molecular weight non-aromatic compounds into higher molecular weight aromatic compounds utilizing a nickel-promoted zeolite catalyst with a SiO2/Al2O3 ratio greater than 5. The nickel zeolite catalyst is subjected to thermal or hydrothermal treatments which results in a decrease in the amount of carbon deposited and a catalyst which resists thermal degradation of regeneration and retains a greater portion of its original activity even after several regenerations.
U.S. Pat. No. 6,420,295 discloses a catalyst composition for use in converting hydrocarbons of a mixture of a zeolite and a binder that has first been calcined and then combined with a promoter compound in the presence of a complexing ligand. The binder is silica or alumina, the promoter compound contains zinc and the complexing liquid is ethylenediaminetetraacetic acid or a salt thereof. A regeneration procedure calcining in air to burn off deposited coke and other carbonaceous materials, such as oligomers or polymers, preferably at a temperature of about 300 to about 1000° C. The optimal time periods of the calcining depend generally on the types and amounts of deactivating deposits on the catalyst composition and on the calcination temperatures.